The objective of this study is to test the hypothesis that sequential therapy with intravenous CP-116.517 followed by oral CP-99.219 has similar efficacy to intravenous ciprofloxacin plus ampicillin followed by oral ciprofloxacin plus amoxicillin for the treatment of community acquired pneumonia which requires initial hospitalization. A secondary objective is to compare the safety and toleration of the two regimens. A total of 320 patients, aged 16 or more with a medical history and clinical and radiological findings consistent with a community acquired pneumonia which requires hospitalization and initial intravenous therapy will be included.